Disk having an underlayer that includes a plurality of nonmagnetic layers interleaved with magnetic layers
View Patent ↗A magnetic disk includes a substrate, a soft magnetic underlayer disposed over the substrate, and a media layer disposed over the underlayer. The underlayer includes a plurality of magnetic layers each containing FeCoN having an atomic concentration of iron that is greater than an atomic concentration of cobalt, and has an atomic concentration of nitrogen that is less than the atomic concentration of cobalt. The atomic concentration of nitrogen is less than eight percent. The underlayer includes a plurality of nonmagnetic layers that are interleaved with the magnetic layers. Each of the nonmagnetic layers has a thickness that is less than one-tenth that of an adjoining layer of the magnetic layers. The media layer contains a magnetically hard material having an easy axis of magnetization oriented substantially perpendicular to both the media layer and the underlayer.
1. A magnetic disk comprising:
a substrate;
a soft magnetic underlayer disposed over the substrate, the underlayer including a plurality of magnetic layers each containing a FeCoN alloy consisting of iron, cobalt, and nitrogen, and having an atomic concentration of iron that is greater than an atomic concentration of cobalt, and having an atomic concentration of nitrogen that is less than the atomic concentration of cobalt, the atomic concentration of nitrogen being greater than zero and less than eight percent, the underlayer including a plurality of nonmagnetic layers that are interleaved with the magnetic layers, each of the nonmagnetic layers having a thickness that is less than one-tenth that of an adjoining layer of the magnetic layers; and
a media layer disposed over the underlayer and containing a magnetically hard material having an easy axis of magnetization oriented substantially perpendicular to both the media layer and the underlayer.
2. The disk of claim 1 , wherein the nonmagnetic layers are formed of chromium or ruthenium.
3. The disk of claim 1 , wherein the thickness of the nonmagnetic layers is in a range between about eight angstroms and twelve angstroms.
4. The disk of claim 1 , wherein the underlayer has substantially zero net magnetic moment.
5. The disk of claim 1 , wherein the nonmagnetic layers are made of a metal that induces antiferromagnetic exchange coupling between a pair of adjacent magnetic layers.
6. The disk of claim 1 , wherein the nonmagnetic layers are made of a metal oxide or nitride that induces antiparallel magnetostatic coupling between a pair of adjacent magnetic layers.
7. The disk of claim 1 , wherein the metal oxide or nitride comprises aluminum oxide, tantalum oxide or aluminum nitride.
8. The disk of claim 1 , wherein the nonmagnetic layer is Cu, Ti, Ta or NiCr.